Over the past few weeks, a whole string of big pronouncements have been made on energy policy – very few of them from the secretary of state for energy. At prime minister's questions last month, David Cameron vowed to force energy firms to give customers "the lowest tariff". Since his appointment as environment secretary, Owen Paterson's statements on energy have been scrutinised – such as his proposal this spring that fracking for shale gas should be fast-tracked. Then there is junior energy minister John Hayes, who said of onshore windfarms a couple of weeks ago that "enough is enough".

All these statements have two things in common: they were made by the Conservative end of the coalition; and they have all been disavowed or shouted down by colleagues. Before the end of this month, the man formally in charge of energy policy, the Liberal Democrat Ed Davey, will set out what the government actually plans to do. After all the chopping and changing and copious hot air from his colleagues, he will have a tough job.

The politics of this are not incidental; they are fundamental. The Conservatives and the Lib Dems face in two different directions, as ministers on the respective sides freely admit. These gusts of uncertainty would make setting policy in any area difficult; in energy, it makes it almost impossible. Investors in a costly nuclear power station or offshore gas field expect repayment over the coming decades, not the next few years: the prospect of big changes to regulation means they are unlikely even to part with their cash. No wonder then that last month seven of the biggest nuclear and electricity firms in the world threatened to change their British investment plans because of heightened "political risk".

Tory MPs have two big worries: they don't want their rural constituencies plastered with windmills, and they don't want higher fuel bills. The latter point is perfectly fair – except one excellent way to keep costs down would be for Britain to have more of its own energy supply, and one of the cheapest forms is onshore wind.

At best, the energy secretary may win the Tories over to a general agreement that investing in energy provides a boost to construction, engineering firms and jobs – with much of the money coming first from the private sector, then from bill-payers (after 2017). But businesses want actual targets for, say, taking carbon out of power generation by 2030 – an "inflexible target" abhorred by George Osborne. If Mr Davey secures that in the energy bill, he will have scored a distinct win for his department – and for the Lib Dems. And that makes this month's battle over energy policy a vital test of coalition relations.